Current supplied to cells of electrochemical plants, with particular reference to metal electrowinning or electrorefining plants, may be apportioned to the individual cell electrodes in a very diverse and inhomogeneous way, negatively affecting the production. This kind of phenomena can take place due to a number of different reasons. For instance, in the particular case of metal electrowinning or electrorefining plants, the negatively polarised electrodes (cathodes) are frequently withdrawn from their seats in order to allow harvesting the product deposited thereon, to be put back in place later on for a subsequent production cycle. This frequent handling, which is generally carried out on a very high number of cathodes, often brings about an imperfect repositioning on the bus-bars and far from perfect electrical contacts, also due to the possible formation of scales on the relevant seats. It is also possible that product deposition takes place in an irregular fashion on the electrode, with formation of product mass gradients altering the profile of cathode surfaces. When this occurs, a condition of electrical disequilibrium is established due to the anode-to-cathode gap which in fact is not constant anymore along the whole surface: the electrical resistance, which is a function of the gap between each anode-cathode pair, becomes variable worsening the problem of unevenness in current distribution. Such phenomenon is often observed, for example, in the case of copper wherein a lesser deposition takes place in the upper part of the cathodes, where a greater amount of gas is present causing an increase in the electrical resistance.
Another problem, particularly common again in the case of copper, is the occasional formation of dendritic deposits, growing locally as faster as the local anode-to-cathode gap decreases, until establishing a short-circuit condition. In the event of a short-circuiting, current tends to concentrate on the short-circuited cathode subtracting current to the remaining cathodes and seriously hampering production, which cannot be restored before the short-circuited cathode is disconnected from the cell.
An uneven distribution of current also generates a loss of quality and production capacity, as mentioned above, challenging the integrity and lifetime of anodes of modern conception manufactured out of titanium meshes.
In industrial plants, given the high number of cells and electrodes present, the tasks of maintaining a uniform deposition, preventing short-circuits or reducing anode damage due to short-circuiting are of high complexity and difficult practical execution.